use of double past tense in a sentence

Question

The use of double past tense is always a bit problematic for me.

So far I have learned that when there is a time reference and two actions happening in past we use past and past perfect. The action which is more past or started earlier it takes past participle, the later one in past tense

ex: When I reached the station the train had already left

This is an example of an adverbial clause with a clear time reference. But my question

1) Is it possible to use two past indefinite tense in the same sentence in a principal-subordinate clause structure?

2) Is it possible to use past-past perfect time frame in the same sentence in a co-ordinating clause structure?

For example, if there's a sense of simultaneous action happening in the past, it doesn't make sense to use the past participle.

I can think of an example given below ( which may be wrong)

She emanated ebullience as she learnt/had learnt about her first rank in the examination.

My thought process was. Knowing the rank and being happy is a simultaneous action--> learnt p.s FOLLOWING UK english

Answer 1

Short answer, yes this is perfectly valid.

She emanated ebullience as she learnt about her first rank in the examination.

Adding the had would imply that she learnt previously and continued to emanate ebullience. I.e.

She [continued to] emanated ebullience since she had learnt about her first rank in the examination.

I do believe you are correct to use learnt. Both learnt and learned are actually valid. Learnt is much more common in the UK. OED